During the use of a complex patient treatment apparatus; for example, the handpiece used when performing ophthalmic surgery, the control of a variety of different subsystems such as pneumatic and electronically driven subsystems is required. Typically, the operation of the subsystems included in a complex patient treatment apparatus is controlled by a microprocessor-driven console. The microprocessor controls within the console receive mechanical inputs from either the operator of the treatment apparatus or from an assistant. A control input device, generically known as a footswitch, is often used for receiving mechanical inputs. These mechanical inputs originate from the movement of the foot of an operator to govern the operation of a subsystem within the patient treatment apparatus. The mechanical inputs from the movement of the foot of the operator are translated into electrical signals which are fed to the microprocessor controls. The electrical signals are then used to control the operational characteristics of a subsystem in a complex patient treatment apparatus.
Examples of footswitches that are designed for receiving mechanical inputs from the movement of the foot of an operator of a complex patient treatment apparatus may be found in U.S. patents, including U.S. Pat. Nos. 4,837,857 (Scheller, et al.), U.S. Pat. No. 4,965,417 (Massie), U.S. Pat. No. 4,983,901 (Lehmer), U.S. Pat. No. 5,091,656 (Gahn), U.S. Pat. No. 5,268,624 (Zanger), U.S. Pat. No. 5,554,894 (Sepielli), U.S. Pat. No. 5,580,347 (Reimels), U.S. Pat. No. 5,635,777 (Telymonde, et al.), U.S. Pat. No. 5,787,760 (Thorlakson), U.S. Pat. No. 5,983,749 (Holtorf), and U.S. Pat. No. 6,179,829 B1 (Bisch, et al.), and in International Patent Application Publication Nos. WO 98/08442 (Bisch, et al.), WO 00/12037 (Chen), and WO 02/01310 (Chen). These aforementioned patents and patent applications focus primarily on footswitches which include a foot pedal or tiltable treadle similar to the accelerator pedal used to govern the speed of an automobile. The movement of the foot pedal or tiltable treadle typically provides a linear control input. Such linear control inputs may be used, for example, for regulating vacuum, rotational speed, power, or reciprocal motion.
In more complex footswitch assemblies, side or wing switches are typically located on a housing on either side of the foot pedal or tiltable treadle. The condition of these side or wing switches is changed by the application of pressure from the front portion of the operator's foot or from the rear portion of the operator's foot. However, given the ever-increasing complexity of patient treatment apparatus, there remains a need in the art to provide yet additional control features on a footswitch, while, at the same time, not making the construction or operation of the footswitch overly complex. It has been found that one of the most usable additional control features for a footswitch would be a second separate proportional control input in addition to the linear control input provided by a single foot pedal or tiltable treadle. There is also a need to assure that the footswitch is ergonomically sound to minimize fatigue of the operator's foot or leg, as such fatigue may cause improper control inputs. Such improper control inputs have the potential of injuring a patient.